This invention pertains to a uniquely shaped transmission/reception antenna which is characterized by compact size, and extremely high-gain, high-efficiency operation given its small size. While the proposed antenna, as has just been stated, is operable in both transmission and reception operating modes, a preferred embodiment of the invention is described herein in a reception-mode setting, wherein it has been found to have particular utility, as, for example, in the reception of satellite-transmitted signals.
A fundamental problem which characterizes prior art antenna designs, for example for high-frequency (multiple gigahertz) operation, is that they are usually extremely large in their intended environment, and function with relatively low gain and low efficiency. Ubiquitous in the genre of such antennas, like satellite-transmission/reception antennas, are the so-called parabolic dish antennas which are extremely large, typically, and bulky and expensive.
A general object of the present invention is to provide a unique form of antenna, of the type generally suggested above in the opening paragraph, which significantly overcomes the principal deficiences of prior art antennas like those just mentioned.
More particularly, an object of the invention is to provide a relatively low-cost, extremely compact antenna which, in relation to its compactness, is capable of extremely high-gain, high-efficiency (the ratio: actual gain/theoretical gain).times.100 operation.
I have discovered that through the careful mathematical shaping of a solid-body polystyrene material, such as the material known as Q200.5 "Polypemco", distributed by Emmerson & Cummins, it is possible easily to realize the principal objects of the invention, just set forth above.
In the description which follows below of my new antenna, I use the terms "nearfield" and "farfield". By these terms, I mean the following: farfield electromagnetic radiation is that which appears to occur over huge distances, wherein radiation "wavefronts" appear to be substantially planar. Nearfield radiation is that which appears to occur relative to an object which is extremely close, for example, within one-half to one-quarter wavelength of the associated operating frequency. In this kind of a setting, radiation wavefronts are strictly nonplanar, and in particular, are extremely curvilinear.
Antennas which are designed in accordance with the disclosure herein, are capable of operating with gains of up to about 40-db, and efficiencies as high as about 85-percent.
According to a preferred embodiment of the invention, which is illustrated in the drawings and described below, the proposed antenna, when viewed from the outside, has what might be thought of a saucer-like outside appearance. The antenna is formed with a body of revolution which includes three main functional portions:
1. An outwardly flared and inwardly converging converter portion extending between front and back planes, wherein what may be referred to as a farfield response occurs in the outwardly facing front plane, and a nearfield response occurs adjacent the back plane;
2. A terminator portion which is joined integrally with the converter portion to provide constant-impedance termination for the converter portion, with the terminator portion characterized by inside and outside curved convergence progressing away from the converter portion; and
3. A coupling-impedance transformer portion having a cylindrical outside, and a curved, convergent inside, which serves to match the overall antenna to the impedance of a selected coaxial port in an external electrical circuit.
Further included in the antenna is a ring-like driven element which resides at the interface plane between the converter and terminator portions--the central plane in the antenna. This ring couples through an axial conductor, and through the transformer portion, to a port of the type mentioned above. Distributed over the radially outwardly facing outside surface of the antenna is a conductive electromagnetic/electrostatic shield.
These and other features, objects and advantages relating to the invention will become more fully apparent as the description which now follows is read in conjunction with the accompanying drawings.